The invention relates to a valve system for regulating a heat-transferring system, in which the valve member can be adjusted by means of an electrical actuating member.
Regulating valves of this kind are frequently employed in cooling circuits in which it is desirable to maintain a system temperature within a range of tolerable operating temperatures. The electrical actuating member drives the valve member through a range varying from fully closed to fully open in order to adjust the amount of coolant flowing through the circuit and to maintain a system temperature within a preferred range. The electrical actuating member may be controlled through various means, including thermostatically, manually, or through automatic computer control. Valve systems of this type are well known in the art and take many different forms depending on the particular type of flow regulation needed.
The principal drawback of these systems, however, is in the potential for loss of control over the electrical actuating member. Such a loss of control might occur for a number of reasons, such as loss of electrical current, damage to the drive motor, failure of an automatic control, loss of communication between control and drive, or some other defect in the system. The loss of control may lead to a system temperature in excess of the tolerance of the system, which in turn leads to damage either to the cooling system itself or to the object to be cooled. It is therefore desirable to employ a system through which it is possible to drive the valve independently of any electrical energy source.
It is accordingly an object of the invention to provide a regulating valve for a heat transferring system which will substantially avoid faulty operation even in the event of a loss of electrical current or errors in the transmission of control signals. A more specific object is to provide a regulating valve that is primarily adjustable by means of an electric drive, but comprises a secondary, failsafe, non-electric drive that prevents faulty operation or, at a minimum, mitigates its effects, even in the unavailability of the primary control.
In order to meet this object, the present invention provides a valve system for regulating a heat transferring system which comprises a valve member in combination with both an electrical actuating member and a secondary actuating member that operates thermostatically to drive the valve. This secondary actuating member is generally exposed to the regulated medium and is designed to react at a predetermined temperature of the regulated medium. When the temperature of the regulated medium is above a predetermined level, the secondary actuating member drives the valve into a position such that overheating of the system is prevented.
Because the drive function of the secondary actuating member is controlled thermostatically and independently of the primary actuating member, the present invention provides a safety function that is completely independent ofxe2x80x94and immune to the failure ofxe2x80x94the primary, controlled drive. Damage to the system is prevented by predetermining a temperature, somewhat below the maximum tolerable operating temperature, above which the thermostatic actuating member will operate to force the cooling of the system, preventing the system from exceeding the maximum tolerable operating temperature.
In one embodiment, the valve member is a rotary slide valve, which rotates about a shaft. The thermostatic actuating member is positioned within the flow of the regulated medium (and thus is sensitive to the temperature of that medium) and further positioned to drive an arm attached to the shaft of the rotary slide valve. During normal operation, the electrical actuating member drives the rotary slide valve independently of the thermostatic operating element. However, if the predetermined temperature should be exceeded, such an exceptional condition indicates a possible failure of the electric drive itself, loss of control over the electric drive, or some other failure which necessitates override of the electrical drive. In the event of such an override condition, the thermostatic actuating member drives the arm of the shaft and forces the rotary slide valve into a fully open position. The rotary slide valve can only be retracted from this position when the reaction temperature has again fallen below the predetermined level.
In another embodiment of the invention, the thermostatic actuating member is positioned between the electrical actuating member and the valve member. During normal operation, the thermostatic actuating member is in a retracted position, but because of the arrangement of the members, transfers the force generated by the action of the electrical actuating member to the valve. If a predetermined temperature is exceeded, the thermostatic actuating member generates an additional drive movement, which drives the valve member into its open position.
In still another embodiment of the present invention, the thermostatic actuating member is positioned such that, during an override condition, it drives the valve directly rather than by means of a shaft arm. Such a configuration enables the thermostatic actuating member to drive the valve independently of the operation of the electrical actuating member or of the presence of any particular elements of the electrical actuating member.
In still another embodiment of the invention, the thermostatic operating element is positioned within a mixing chamber, into which fluid from multiple inlets is communicated. Typically, one inlet will communicate hot fluid (such as fluid returning from cooling an internal combustion engine) and another will communicate cooled fluid (such as from a radiator or a reservoir) into the mixing chamber. The valve member is designed to permit hot fluid, cooled fluid, or a combination of the two to flow into the mixing chamber. The thermostatic actuating member is positioned such that, during an override condition, it drives the valve so as to increase the flow of cooled fluid and decrease the flow of hot fluid into the mixing chamber.
Further characteristics and advantages of the invention may be observed from the subsequent description of the embodiments represented in the drawings.